Field of the Invention
This invention relates to improvements to a stock feeder which repetitively advances uniform segments of stock material into a production machine, which in turn, performs work on the segments. Specifically, the invention relates to an improvement to the movable feed carriage of such stock feeders.
Automatic stock feeders have been used with production machinery to attain relatively high production rates of articles manufactured from stock material which is wound on a spool or a roll. To handle the material on the spool or roll, as the case may be, some conventional feeders employ at least one set of clamps to grip and pull periodically during feeding, and another set of clamps to hold the stock material in place while the production machine works on a segment of the material to form an article of manufacture. When handling relatively narrow stock material, the feeder might employ single gripper or clamp for each of the pulling and holding operations, but for relatively wide stock material, say 12 inches or more, a pair of clamp assemblies usually are used at each end of the feeder. Some of the older types of feeders employ opposed rollers, instead of clamp assemblies to perform these functions, but due to the occasional slippage which occurs between the stock material and the rollers, these types of roll feeders have not proved as efficient and reliable as grip feeders.
Production operations performed by the machine may involve forming, cutting, milling, stamping, machining, etc., and the stock material from which the article is manufactured may comprise of wire, metal tubing, sheet metal, bar steel, etc., or even non-metallic stock material such as a plastic or fiber material. The feeder itself may be constructed in a fashion to handle one particular size of stock material, or it may be adjustable over some dimension thereof to handle, for example, stock material of different dimensions. Obviously, if a production machine is to have versatility in being able to produce a variety of articles, the stock feeder which supplies it with segments of stock material should also be versatile in that it should be capable of handling material of different widths and thicknesses.
Furthermore, in order to improve the efficiency of manufacturing operations, it is desirable to operate the production machinery at high speeds in order to increase production yields and yet maintain the same quality of production without destruction or deterioration of the machine due to wear and tear. In order to attain such high operating speeds, it is required that the control functions of the feeder (i.e., the gripping, releasing, and feeding) be harmoneously controlled at synchronized time instances.
To reduce the force of impact between the movable carriage and its limit stops, U.S. Pat. No. 3,753,522 discloses a mechanical feeder for advancing uniform segments of stock material, which feeder includes in a movable feed clamp carriage, a double acting air cylinder and piston assembly which acts as a mechanical decelerator for the carriage as it comes into the proximity of the forward and rearward stroke positions of the carriage. The feed clamps and the hold clamps operate pneumatically. In its operation, the air pressure which operates pneumatic valves for the hold and feed clamps is also supplied to the double acting piston/cylinder assembly at each extreme end of the stroke for effecting mechanical deceleration of the carriage. The double acting piston couples a rod on the movable carriage and the rod engages stops located at a front portion of the frame and on an adjustable stop bar located at the rearward stroke position. The adjustable stop bar establishes the rearward position of the stroke. Each clamp assembly embodies its own separate double acting piston/cylinder assembly. This device may have limitations in the extent to which the valving operations may be synchronized with carriage movement due to the provision of separate double acting pistons and lack of adjustability of forward limit stops against which the double acting rods abut.
U.S. Pat. No. 4,059,212 assigned to the assignee hereof describes a stock feeding device, similar in some respects to the operation of the device of the subject invention, but possesses only a single feed clamp actuator and a single hold clamp actuator for feeding and holding relatively narrow stock material.
In view of the foregoing, it is an objective of this invention to provide a stock feeder which can be operated at higher speeds without attendant synchronizing problems of prior art feeders thereby to increase production yield of a production machine to which the feeder is coupled.
Another objective of this invention is to provide a stock feeder including means to more effectively profile the slowdown of the movable feed carriage at its forward and rearward limits of the stroke path thereby to enable the feeder to operate at higher speeds without losing timing synchronization between the movement of the carriage and the operation of the hold and feed clamps.
A further objective of this invention is to provide a stock feeder for automatically and repetitively feeding uniform segments of stock material, which feeder is more economical, reliable and simple in construction than prior art devices.